1. Field of the Invention
The invention relates to a method and an arrangement for improving the combined use of different satellite navigation systems and a receiver system for a combined use of different satellite navigation systems.
2. Discussion of Background Information
By the combined use of two different satellite navigation systems the precision, visibility and availability can be considerably improved. However, different satellite navigation systems normally use different representations of the international atomic time scale TAI (Temps Atomique International), whereby the system times of different satellite navigation systems generally differ. For example, NAVSTAR-GPS or GPS uses the GPS system time, GLONASS, however, uses the GLONASS system time differing therefrom. Another important difference lies in the geodetic reference systems, on which the satellite navigation systems are based. For example, information of the satellites with GPS are given in the World Geodetic System 1984 (WGS 84), with GLONASS in the Soviet Geodetic System 1985 (SGS 85). For a combined, in particular global use of different satellite navigation systems an equalization of the differences in the reference systems and in the time scales is therefore necessary in order to obtain the most exact positioning solutions.
The differences between the reference systems are normally relatively small compared to the difference in the system times. It is therefore provided for a combined use of GPS and the future European satellite navigation system Galileo only to broadcast a model for the difference between the system times of the two systems. However, even after taking this model into consideration, the error that is caused by the different time systems is still significant. For a combined use of GPS and Galileo, but also quite generally of different satellite navigation systems, to achieve the most exact possible position determination, it is accordingly important to reduce this error.